Servo-brake mechanism for vehicles and the like



y 1939- a. R. G. GATES 2,16

SERVO-BRAKE MECHANISM FOR VEHICLES AND TH LIKE FiledApril 26, 1937 2 Sheets-Sheet 1 KO Q; Q m m n;

W5 3 2 Q Ox INVENTOR o y/fiaaaw A 7TORNE Y July 18, 1939. GATES 2,166,585 I SERVO-BRAKE MECHANISM FOR VEHICLES AND THE LIKE Filed April 26, 1937 2 Sheets-Sheet 2 64 63 INVENTOR ATTORNEY Patented-July 1 8, 1 939 UNITED STATES PATENT OFFICE f' SERVO-BRAKE MECHANISM FOR 'vEmoLEs AND THE LIKE Geoffrey Robert Greenbergh Gates, London, Eng-- land, assignor of one-half to Automotive Products. Company Limited, London, England Application Amines, 1937, Serial No. 139,078

In Great Britain May 7, 1936 7 Claims.

clutch employed in such mechanism at a speed .corisiderably lower than that of the part from which it derives its motion, reduction gear being employed for this purpose.

The present invention has for an object to avoid the necessity for the employment of reducton gear or at least to enable a high ratio gear to be used; to provide an improved servo'motor' or clutch of the friction type for use in servo brake mechanisms of the typereferred to, the

driven member or members of which may run at" the same speed as, or at a speed but slightly less than, that of an existing, e. g., road wheel driven or engine driven, part, without undue temperature rise of the friction surfaces; and to pro- 1 vide a simple and robust construction of servo "clutch which shall be inexpensive to manufacture and reliable in use;

. According,,to the invention,- in a servo brake m chanism of the type. referred to the servo "clutch has two sets of platesQthe plates of one 1 set being of substantially greater diameter than those of the other, and the outer parts of the "35 first set of plates serve as cooling fins for the radiation of, at generated within the device.

Preferably, hese outer parts of the first set of plates are utilized for connecting the plates of this settto rotate as one, the plates of the other set being in splined or equivalent relationship with a shaft extending concentrically there-' through, these latter plates being, in general, the driving plates of the device..

Owing to the eifective cooling'aflorded by the 46 outer parts of one set' of plates which will be ;formed preferably of metal the smaller diameter or driving plates may be in splined or equivalent relationship with the propeller shaft of a vehicle or with a shaft running at the same speed as,v

to or at aJspeed but slightly less than, that of the propeller shaft.

'Ijhe invention is illustrated in the accompanying drawings, in which:

Figure 1 shows more or less diagrammatically an arrangement for transmitting an effort from shaft ofa a, servo clutch to a brake actuating member in accordance with the invention.

Figure .2 is a similar view showing a modified arrangement. v

Figure 3gshows a form of clutch and cooperat- 5 ing parts constructed-in accordance with the invention'.

Figure 4 is .a section on line 44 of Figure 3.

Figure 5 is a broken view in longitudinal sec,- tion, partly in elevation, of clutch operating means, the line of section being on line 5 5 of Figure 6.

Figure 6 isa section online 8-6 of Figure 5. As shown. in Figures 3 and 4, a shaft H, which may be driven from the propelleror other vehicle to which the device is fitted, extends through bearings 12, 13 and carrieson an enlarged overhanging ,portion 14 thereof two sets of clutch plates, one set 15 being of smaller diameterthan those l6.of the other set, the plate 15 being in splined relationship with the enlarged portion ll of the shaft 1| and the outer parts of the plates 16 being formed as cooling fins and having extending therethrough a number of rods,

one of which is indicated at .11, which connect }said plates 16 to move angularly as one with.

one another, with a driven member 18, and with -a casing 19; this assembly comprising the parts l9, l1 and 18 being journalled in bearings 80 and Bl in a stationary casing, indicated generally at -8'2. The casing 82 will .becut away, as indicated .at 83 to allow air to circulate freely over the outer'cooling fin portions of the plates 16. .The casing 19 has formed integrally therewith a slave cylinder 84 receiving fluid from an annular 3 space, indicated at 85, between two' glands 86 which are located between a fixed spigot 81 and the cylindrical portion 88 of-the casing 19; this fixed spigot 81 being formed with a coaxial bore 88 from which radial bores extend tothe annular space 85. A piston 90 in the sleeve cylinder 84 is located resiliently in an axial direction by awasher 8| engaging in 'a peripheral groove in the piston 80, and also in a peripheral groove in'theouter wall of the cylinder 84, and

'the cylinder 84 the piston!!!) col-operates with the rocker. 92 at one side thereof and brings it to bear-at its other side against an end driven clutch member 94 whichis thickened to act' as a thrust member. It willbe seen that with this construction, involving a swivel orrotaryliquid connection to a slave cylinder moving with the 5 rotate continuously a flexible conduit or hose may be used to establish liquid connection with the slave cylinder which moves with the driven clutchplates. p

In cases where a rocker, such asjl of Figures 5 and 6 and 92 of F1 res 3 and 4, is employed it is desirable wit a view to ensuring that this rocker arrangement shall always be eflective in preventing .the' undesirable oscillatory or swash plate movement of the clutch plates that theeflort should be applied to this rocker and that the rocker should be connected with the load at diflerent distances from its fulcrum such that there will always be a substantial reaction at said'fulcrum. Preferably, the arrangement is such, as shown in the drawings, that the magnitude of the reaction of the fulcrum will be of the same order as that of the force applied to the load by the rocker and of the effort applied tothe rocker. This substantial reaction at the fulcrum of the rocker prevents any slight vibratory movement thereof.

about an axis transversely of the fulcrum which would be possible even where the pivoting or fulcruming of the rocker is carried out with very small clearances. Any clearance at the fulcrum is, so to speak, nullified or rendered in-' capable of permitting such vibration by the sub- 'stantialreaction at the fulcrum. It will be further noted that as a material and important construction in preventing undesirable oscilla- 'tory or swash plate movement of the clutch plates that the fulcrum length by which the rocker level Si is supported is at least substantially equal to or of the order of the distance between the points (rollers' 66) at which the.

rocker lever applies pressure to the clutch plates.

For imparting an effort from the servo clutch to a brake-actuating member, such as the piston of the master cylinder of, hydraulic or fluid the groove 3|, and this chain or other flexible member 3! lies at its other end within a groove 1 34 of an axially fixed nut 35 to which it is an-.-

chored by a pin 36 similar to the pin 33. This nut is in threaded relationship with a non- (not shown) constituting or cooperating with a .i-.,brak e-actuating member to which latter brakeapplying movement is imparted by rotation of the nut 35 in the direction of the arrow (Figure 1),,- arid it will be seen that such rotation is impar'tedf'to the nut 35'by angular movement of the ,dniven clutch member 13 in either dlrect'ion; Altematively (see Figure 2) a driven clutch member, such as 13 (Figure 3) may be formed as a cam 31 having a follower "which transmitsmotion to a thrust member or brakeapplying member (not shown). will be seen'that motion in the same direction is Here again it imparted to the latter member by angular movement of the cam clutch member 31 in either direction.

The light engagement and consequent drag of the elutchmentioned above insures that in the case of Figure .1 the-chain or flexible member 32 shall be taut, or in the case of Figure 2, that the cam 31 shall always be pressing lightly upon the follower 33 irrespective of whether a yehicl to which the brake mechanism is fitted is sures also that immediately proper engagement with the clutch is brought about the brake-actuating member will be shifted, thus avoiding'any time lag in the application of the brakes which might otherwise be occasioned by the tightening of the chain or flexible member 32 (Figure 1) or by the cam 31 of Figure 2 being brought into firm engagement with the follower-33.

To avoid oscillation of the clutch plates, means may be employed such as shown in, Figures 5 and 6 of the drawings. This means includes a thrust member 5! which cooperates with the outer driving clutch plate, indicated at 53, splined upon a shaft 53 and into which rods, indicated at 34, connecting the driven clutch plates (not shown) extend, may carry a bearing member 33 through which clutch-engaging pressure is transmitted to the thrust member ii. in this case, a single slave cylinder 56 containing a piston 51, cup washer 58, and spring 53 is located some distance from the bearing member 55 and thrust member 54, and there is disposed between the bearing member 33 and the piston 31 a thrust rod 3|) and an inverted U-shaped rocker 6| straddling the shaft 53. This rocker II is pivoted at the ends of its links by pins 33 extending inwardly from the latter into bores formed to receive them in a plate 63 retained in position by studs 63 and carries on two further pins 9, pair of rollers 86 which cooperate with the bearing member 55. The thrust rod 3|) cooperates with the rocker ii at the top thereof. It will be seen that as the piston 31 is moved by the introduction of 'liquid under pressure into the cylinder 36, the rocker 3| will be rocked about the pins 32 as fulcrum and will bring the rollers 66 to bear upon the bearing member ii at opposite sides of the latter. v

What I claim to be new is:

.1. A servo brake mechanism of the type referred to, including a multiple plate clutch comprising one set of plates rotatable with ashaft extending concentrically therethrough, a second set of plates, a driven carrier to which the second set of plates are connected, the plates of one set being of substantially greater diameter than the plates of the other set and constituting at their outer parts cooling fins for dissipatingythe heat generated in' the clutch, fluid pressure means for engaging said sets of plates to impart an angular movement to the carrier, and means for utilizing such angular carrier movement. to apply the brakes of the yehicle, the fluid pressure engaging means including a rocker lever fulcrummed about an axis transversely to that :of the clutch and operating to transmit engaging pressure to the I clutch plates.

2. A servo brake mechanism as defined in claim" 1, wherein both sets of clutch plates are conin the fluid pressure engaging means includes a ll slave cylinder and wherein said slave cylinder is single slave cylinder responsive to fluid pressure and acting on the rocker lever.

4. A construction as defined in claim 1, wherein the fulcrum of the rocker lever is less distant from the point at which the rocker lever applies pressure to the clutch than the latter point is from the point at which operating pressure is applied to the rocker lever, whereby the reac-' carried by a casing movable as a unit with the driven clutch plates and means for admitting a source of liquid under pressure to the slave cylinder.'

7. A servo brake mechanism including a driven shaft and the other set of plates being free of but concentric with the shaft, a carrier connected to and movable withthe plates free of the shaft, a slave cylinder mounted in the carrier, and a shaft, a multi-plate clutch mounted on the shaft,

one set of plates having splined relation to the rocker lever arranged between the slave cylinder and clutch plates and acting in the operation of the slave cylinder to exert clutching pressure between the respective sets of plates, a fixed conduit for the admission of fluid under pressure, a chamber surrounding and open to the conduit, and a communication between the chamber and the slave cylinder to maintain constant fluid pres- 5 sure service to the slave cylinder.

- GEOFFREY ROBERT GREENBERGl-I GATEJS. 

